As air travel has increased over the past decades, airport facilities have become more crowded and congested. Minimizing the time between the arrival of an aircraft and its departure to maintain an airline's flight schedule, and also to make a gate or parking location available without delay to an incoming aircraft, has become an airline priority. The safe and efficient ground movement of a large number of aircraft simultaneously into and out of the ramp and gate areas has become increasingly important. As airline fuel costs and safety concerns and regulations have increased, the use of the aircraft main engines is no longer the best option for achieving the desired safe and efficient ground movement.
Various alternatives to the use of an aircraft's main engines to move an aircraft on the ground are available and have been tried. The use of a tug or tow vehicle to move an aircraft into and out of a gate or parking location can eliminate the need to use the aircraft main engines. This option, however, is not without its own challenges and costs. More ground vehicles, requiring more fuel and more ground personnel to operate them, add to an already congested environment in the gate area. Restricted use of the aircraft engines on low power during arrival at or departure from a gate is an additional option. This option is also problematic, however. Not only does engine use consume fuel, it is also noisy, and the associated safety hazards of jet blast and engine ingestion in a congested area are significant concerns that cannot be overlooked.
The use of a motor structure mounted in connection with a wheel to rotate the wheel and drive a vehicle, including an aircraft, has been proposed. The use of such a structure, ideally, should move an aircraft without the use of an aircraft's main engines. U.S. Pat. No. 2,430,163 to Dever, U.S. Pat. No. 3,977,631 to Jenny, U.S. Pat. No. 7,226,018 to Sullivan, and U.S. Pat. No. 7,445,178, McCoskey et al, for example, all describe drive motors associated with aircraft gear wheels intended to drive an aircraft on the ground. None of the foregoing patents, however, suggests a boltless wheel structure with an integral drive motor assembly. Nor does this art describe a boltless wheel assembly that is configured to maximize the limited landing gear space available to support substantially within the wheel a compact motor assembly capable of powering an aircraft drive wheel that could be easily installed on an existing aircraft.
Many aircraft wheels are made, like the wheel described in U.S. Pat. No. 5,409,048 to Kipp et al, with two sections that are fastened together with appropriate bolts and nuts or other like fasteners. Removal of the wheel for repair or maintenance requires having the proper tools available to remove the bolt or other fastener. Access to the bolts or fasteners may not be easy or may require the removal of other wheel assembly components. One type of aircraft wheel in current use has a circumferentially divided rim, typically with a tire bead flange on the inboard side of the wheel that is formed integrally with the wheel rim. A removable, or demountable, tire bead flange located on the outboard side of the wheel is removed to permit tire changes. A split lock ring seated in the wheel rim maintains separable wheel structures in place during operation of the aircraft. These annular retaining structures may be designed to be kept in place with retaining elements other than bolts or similar fasteners, but may also be secured by bolts. Some type of closure mechanism that can be opened without requiring tools may be fitted on the wheel to apply sufficient pressure on the wheel to keep the wheel sections together. Split compression ring or snap ring wheels were widely used on World War II era aircraft. Their use was essentially discontinued, however, as a result of problems with distortion, cracking, wear, and the like. Tire changes could also be challenging with this type of wheel.
Lock ring assemblies for circumferentially divided and demountable flange aircraft wheels have been proposed more recently, in U.S. Pat. No. 5,086,821 to Russell et al and U.S. Pat. No. 6,786,259 to Vehar et al, for example. Russell et al describe an annular locking ring for an aircraft wheel that distributes stress loading and overall bulk and weight. This arrangement is intended to reduce force distribution and eliminate cracking and excessive wear. Vehar et al describe an improved variation of an aircraft wheel locking ring designed to prevent the locking ring from being thrown from the aircraft wheel in the event of a flat tire or a blowout. A specifically configured retaining key and spring type clip hold the locking rim together in a manner that provides suitable gaps to enable the expansion and contraction of the locking ring.
International Publication No. WO 95/09737 to Allied Signal, Inc. discloses an aircraft wheel demountable flange with a retaining ring sealed by a flexible composite seal. U.S. Pat. No. 6,550,510 to Champion also discloses a demountable flange on an aircraft wheel with a retaining ring configured to have a cross-sectional geometry that is stated to reduce the likelihood of fatigue damage to the wheel rim. None of the foregoing patents or publication, however, suggests that the demountable flange or locking rim wheels disclosed therein could be used effectively on an aircraft wheel assembly that is specifically configured to integrally support within the dimensions of the wheel a drive motor assembly capable of driving the wheel to move the aircraft on the ground.
Published United States patent applications, including U.S. Patent Application Publication Nos. US2006/0273686 to Edelson, US2007/0282491 to Cox et al, US2009/0152055 to Cox, US2009/0261197 to Cox, International Patent Application Publication No. WO 2008/027458 to Cox et al, and British Patent No. 2457144, owned in common with the present invention, describe aircraft drive systems that use electric drive motors to power aircraft wheels and move an aircraft on the ground. These disclosures focus on specific aspects of the drive systems and motor assemblies, including, inter alia, drive system data, motor design, tire profile, and motor cooling, rather than on features of aircraft wheel structures.
A need exists, therefore, for a split circumference, demountable flange, or locking rim aircraft wheel assembly designed to support an integral drive motor assembly completely within the volume defined by the inboard and outboard axial dimensions of an aircraft wheel well that functions efficiently to drive the aircraft wheel and, therefore, the aircraft on the ground. A need also exists for a split circumference aircraft wheel with an integrally supported drive motor that can be easily installed in an existing aircraft landing gear.